1. Field of the Invention
The present disclosure relates generally to methods for compensating negative bias temperature instability (NBTI) effects on transistors.
2. Background Art
NBTI is an electrochemical reaction that causes transistors to degrade in performance over time. For example, NBTI may adversely affect life-time reliability of a transistor, e.g., metal-oxide semiconductor field-effect transistor (MOSFET), when negative bias is applied to the gate terminal of the transistor. This causes the threshold voltage of the transistor to increase and the drive current of the transistor to decrease over time.
The NBTI effects are particularly severe for p-type MOSFETS (PMOS). When the PMOS gate is turned on, NBTI causes the threshold voltage of the PMOS to gradually increase, even under static conditions. Consequently, the current driving capability of the PMOS and overall speed of operation of the device in which the PMOS is utilized, e.g., microprocessor, degrade over time. The resulting frequency loss in the microprocessor leads to direct thread-performance loss. Therefore, NBTI effects on PMOS are an important consideration in optimizing the performance and operational lifetime of transistor devices.